Effects of freezing and hot air drying on the physical, morphological and thermal properties of cranberries (Vaccinium macrocarpon).

The aim of this study was to evaluate the effects of convectional (F) and cryogenic (N) freezing, as well as convective drying (C) temperatures of 60, 70, 80 and 90 °C on the physical, morphological and thermal properties of cranberries. Convectional (F) freezing induced considerable texture modification and cell structure disruption, whereas cryogenic (N) freezing led to freeze cracking. Depending on pretreatment and drying conditions, convective drying of whole cranberries lasted from 5 to 195 h. Freezing significantly increased the rate of moisture removal in the first stage of drying, and it shortened drying time by up to 43%. Convectional freezing combined with hot air drying at a low temperature (60 °C) induced minimal changes in the surface structure of dried samples and produced fruits whose overall appearance was similar to that of unprocessed berries. Cryogenic freezing combined with hot air convective drying contributed to the greatest changes in the properties of cranberries. An increase in air temperature from 60 to 70, 80 and 90 °C shortened the drying time of cranberries by up to 69-97%. However, the increase in drying air temperature was accompanied by structural changes in cranberries. [ABSTRACT FROM AUTHOR]